Aqueous epoxy resin paint composition

ABSTRACT

An aqueous epoxy resin paint composition comprising an epoxy resin emulsion formed by emulsifying a bisphenol type epoxy resin or a mixture of a bisphenol type epoxy resin with an epoxy resin having a compatibility with said bisphenol type epoxy resin and a structure similar to that of said bisphenol type epoxy resin but being quite different therefrom in a part of the structure in water with a polyoxyethylene benzylated phenyl ether having an HLB value of at least 15, and a curing agent and, if desired, a pigment and other additives.

BACKGROUND OF THE INVENTION:

1. FIELD OF THE INVENTION:

This invention relates to an aqueous epoxy resin paint composition. Moreparticularly, the invention relates to a room temperature drying epoxyresin emulsion comprising as the main ingredient an epoxy resinemulsified in water by a non-ionic surface active agent and,incorporating therein, a curing agent and, if desired, a pigment andother additives.

2. DESCRIPTION OF THE PRIOR ART:

Recently, air pollution caused by solvents and the bad influence ofsolvents on the human body have become serious problems, and hence, theimportance of aqueous paints is increasing. Various resin haveheretofore been used for aqueous paints, and epoxy resins are often usedin the field of primer paints in which such properties asrust-preventive property and chemical resistance are regarded asespecially important.

In the art, the following aqueous epoxy resin compositions haveheretofore been known. For example, a composition comprising (1) apolyepoxy resin and (2) a copolymer of an alkyl ester of anα,β-ethylenically unsaturated monocarboxylic acid and an alkyl halfester of itaconic acid is known as an aqueous coating compositionexcellent in alkali resistance, adhesion and storage stability (U.S.Pat. No. 3,238,170). Further, an aqueous emulsion comprising an epoxyresin and a protein acting as protective colloid and an emulsioncomprising a mixture of an amine-epoxy resin condensate and an epoxyresin are known in the art (U.S. Pat. No. 3,020,250 and U.S. Pat. No.3,449,281).

Moreover, research work has heretofore been made on various emulsifiersfor emulsifying epoxy resins in water. For example, in the art are knownan aqueous emulsion of an epoxy resin in which a reaction product of aboric acid ester derived from boric acid with both an alkylene glycoland a β-dialkyl-substituted amino-alkanol is used as an emulsifier (U.S.Pat. No. 3,301,804), a polyepoxide emulsion for electro-deposition inwhich a polyepoxide is emulsified with an emulsifying agent of thephosphate ester type (U.S. Pat. No. 3,634,348), an epoxy resin emulsionfor sizing glass fibers in which a cationic emulsifying agent selectedfrom the group consisting of imidazolines and amides and a non-ionicemulsifying agent are used in combination (U.S. Pat. No. 3,249,412), andthe like.

Also various curing agents for epoxy resin emulsion compositions areknown in the art. For example, as curing agents for epoxy resincompositions, there can be mentioned a polyamide reaction productderived from a polymeric fatty acid and an aliphatic polyaminecontaining terminal amino groups (U.S. Pat. No. 2,811,495 and No.2,899,397), a salted amine derived from a carboxylic acid having 1 to 8carbon atoms and a tertiary amine (U.S. Pat. No. 3,640,926), a polyamidederived from a diamine and a dicarboxylic acid (U.S. Pat. No.3,355,409), a phenol modified polyamine (U.S. Pat. No. 3,383,347), anamino-containing polyamide prepared by reacting a polyamine with apolymerized fatty acid (U.S. Pat. No. 3,324,041), and the like.

A bisphenol type epoxy resin is ordinarily used as a vehicle of anaqueous epoxy resin paint.

The bisphenol type epoxy resin, however, has the fatal defect that theepoxy resin is crystallized when it is stored for 3 months or longerespecially at low temperatures. The cause of this undesiredcrystallization is not yet certain, but in view of the fact that aliquid epoxy resin having a narrow molecular weight distribution rangeis easily crystallized at low temperatures, it is considered that thecrystallization is due to arrangement of molecules having the samestructure. Once crystals are formed in the epoxy resin, they growgradually and finally, they precipitate in the form of particles toopacify the liquid resin. This phenomenon is especially likely to occurif the paint is gradually cooled to about 0°C., and precipitatedparticles are dissolved again under heating. In short, this phenomenonis quite similar to the phenomenon in which inorganic salts arecrystallized from aqueous solutions. Re-dissolving of crystals in anepoxy resin does not, in general, proceed at temperatures approximatingroom temperature. Accordingly, it is very difficult to restore theoriginal state by allowing crystals in the epoxy resin to stand still asthey are, and it is generally necessary to heat the crystal-containingpaint to about 50°C. by external heating or the like. Furthermore, inthe case of an aqueous epoxy resin paint, destruction of emulsionparticles is caused to occur with advance of crystallization, and whendestruction of emulsion particles occurs, it is impossible to restorethe original state even by conducting heating afterwards. Therefore, anaqueous epoxy resin paint has a fatal defect that a once crystallizedpaint cannot be used any more.

The epoxy resin to be used as the main component of the vehicle has theforegoing defects, and in addition, an optimum curing agent for aqueousepoxy resin compositions has not been developed.

For instance, when a polyamide resin having a high amine value is usedas the curing agent, the resulting composition is defective in thatgelation does not occur even after the passage of pot life, and nosatisfactory results are obtained when the curing agent of this type isemployed.

More specifically, even if an ordinary polyamide resin is mixed with anepoxy resin and the resulting composition is applied to a substrate,since hardly any water is evaporated from the coating film underhigh-humidity conditions, almost no gelatin proceeds even after thepassage of pot life but partial gelation alone occurs. In an extremecase, no uniform film is obtained but a powdery film is left. This is adefect observed when a polyamide is used as the curing agent. In otherwords, in the case of an aqueous epoxy resin paint, it is consideredthat if water is present in the coating film, the activity of the curingagent is reduced, and especially under high-humidity conditions, almostno water is evaporated from the coating film and hence, gelation doesnot occur even after the passage of pot life.

In general, an epoxy resin paint is used as a primer paint for use incoating bridges, tanks or the like. However, when it is applied toespecially close surfaces or on the inner face of a tank or the ballasttank of a ship which is in the substantially sealed state, theabovementioned defect is brought about and a sufficiently cured filmcannot be obtained.

A paint excellent in rust-preventive property and chemical resistancehas heretofore been prepared by using a chromate type pigment incombination with an aqueous epoxy resin composition such as mentionedabove. However, in this paint including a pigment of the chromate type,chromium ions are gradually dissolved out from the coating film andthere is a risk of causing environmental pollution.

As is apparent from the foregoing, the conventional aqueous epoxy resinpaints have various defects and when they are used as primer paints ofthe natural drying type, various problems result.

SUMMARY OF THE INVENTION:

This invention relates to an aqueous epoxy resin composition in whichthe above-mentioned defects involved in conventional techniques areovercome.

Objects of this invention are as follows:

1. To prevent crystallization in an aqueous epoxy resin paint duringstorage, especially at low temperatures.

2. To improve the film-forming property under high-humidity conditionsin an aqueous epoxy resin paint composition.

3. To provide an aqueous epoxy resin paint that can give a filmexcellent in corrosion resistance and chemical resistance.

4. To improve chemical and physical properties in a film formed from anaqueous epoxy resin paint.

More specifically, in accordance with this invention, there is providedan aqueous epoxy resin composition characterized in that (I) a resinouscomponent comprising (A) 98 to 50% by weight of a bisphenol type epoxyresin and (B) 2 to 50% by weight of at least one member selected fromnovolak type epoxy resins, epoxy resins of the dimer acid type, epoxyresins of the trimer acid type and methyl-substituted bisphenol epoxyresins is used; (II) a nonionic surface active agent having an HLB(hydrophilic-lipophilic balance) value of at least 15, especially apolyoxyethylene benzylated phenyl ether, is used as an emulsifier; (III)a curing agent composed of a polyamide resin derived from a dimer acidand a polyether diamine or a mixture of said polyamide resin with anaromatic amine compound is used; and that (IV) at least one memberselected from molybdic acid salts of strontium, calcium, potassium, iron(divalent), barium and ammonium is used as an anticorrosive pigment.

DETAILED DESCRIPTION OF THE INVENTION:

The bisphenol type epoxy resin (A) to be used in this invention is anepoxy resin obtained by condensation between bisphenol A[2,2-bis(4'hydroxyphenyl)-propane] and epichlorohydrin, and iscommercially available. Commercially available bisphenol type epoxyresins are liquid or solid and have a molecular weight of about 350 toabout 3750 and an epoxy equivalent of about 180 to about 3500. Typicalinstances of these commercially available bisphenol type epoxy resinsare as follows:

1. Epikote 815, Epikote 827, Epikote 834, Epikote 1001, Epikote 1004,Epikote 1007 and Epikote 1009 (trademarks for products manufactured byShell Chemical Co.)

2. DER 330, DER 331, DER 334, DER 337, DER 661, DER 664, DER 667 and DER669 (trademarks for products manufactured by Dow Chemical Co.)

3. Araldite GY250, Araldite GY252, Araldite GY260, Araldite GY280,Araldite GY6071, Araldite GY6084, Araldite GY6097 and Araldite GY6099(trademarks for products manufactured by Ciba Limited)

4. ERL 2774 and ERL 2795 (trademarks for products manufactured by UnionCarbide Corporation)

5. Epiclon 850 (trademark for product manufactured by Dainippon Ink andChemicals Incorp.)

These commercially available bisphenol type epoxy resins can be usedsingly, or mixtures of two or more of them can also be employed.

This bisphenol type epoxy resin is used as a vehicle. Use of a liquidepoxy resin is preferred because it is readily emulsified, but when thebisphenol type epoxy resin is solid, it can be emulsified or dispersedin water by mixing it with other liquid epoxy resin to dissolve it or bymelting it under heating.

In this invention, in combination with the above bisphenol type epoxyresin (A) is used an additive resin (B) selected from the groupconsisting of (1) novolak type epoxy resins, (2) epoxy resins of thedimer acid or trimer acid type and (3) methyl-substituted bisphenolepoxy resins.

As the novolak type resin, there can be used those having the followingstructure: ##SPC1##

wherein n is a number of from 0 to 2 and R stands for a hydrogen atom ora methyl, ethyl or propyl group.

As commercially available products of such novolak type resin (1), therecan be mentioned Epikote 152 (product of Shell Chemical Co. having anepoxy equivalent of 172 - 179), Epikote 154 (product of Shell ChemicalCo. having an epoxy equivalent of 176 - 181), DEN 431 (product of DowChemical Co. having an epoxy equivalent of 172 - 179), DEN 438 (productof Dow Chemical Co. having an epoxy equivalent of 175 - 182), EPN 1138(product of Ciba Limited having an epoxy equivalent of 172 - 179), etc.These resins are generally prepared by reacting a novolak type phenolicacid-formaldehyde resin with epichlorohydrin.

The dimer acid or trimer acid type epoxy resin (2) is usually preparedby reacting a dimer or trimer acid with epichlorohydrin (the preparationprocess is disclosed in, for example, Japanese Patent Publication No.7454/62 published on July 7, 1962 by Shell International ResearchMaatochappij N.V., Netherland), and as commercially available productsof the epoxy resin of this type, there can be mentioned, for example,Epikote 871 (product of Shell Chemical Co. having an epoxy equivalent of390 - 470) and Epikote 872 (product of Sheel Chemical Co. having anepoxy equivalent of 600 - 700).

The methyl-substituted bisphenol epoxy resin (3) to be used in thisinvention is a resin having the following structure: ##SPC2##

Wherein n is 0 to 3 and X is hydrogen or chlorine. The epoxy resin (3)is prepared by condensation of β-methyl epichlorohydrin orβ-chloromethyl epichlorohydrin with bisphenol-A. The preparation processis disclosed in, for example, U.S. Pat. No. 3,553,165 (Patented on Jan.5, 1971 by Chiyoda Kako Kensetsu Kabushiki Kaisha).

As a commercially available product of the resin of this type, there canbe mentioned, for example, Epiclon 800 (product of Dainippon Ink andChemicals Incorp. having an epoxy equivalent of 195 - 225).

In this invention, as one means for attaining the object of preventionof crystallization there can be adopted combined use of the abovementioned bisphenol type epoxy vehicle resin with at least one memberselected from the foregoing resins (1) to (3), each of which has acompatibility with the vehicle resin and a structure similar to that ofthe vehicle resin but is different therefrom in a part of the structure.

The additive epoxy resin (1), (2) or (3) is incorporated in thebisphenol type epoxy resin in such an amount that the additive resinaccounts for 2 to 50% by weight of the sum of the bisphenol type epoxyresin and the additive epoxy resin. When the amount of the additiveepoxy resin (1), (2) or (3) is less than 2% by weight, no substantialeffect of preventing crystallization can be obtained, and when theamount of the additive resin exceeds 50% by weight, the salineresistance, water resistance and moisture resistance of the resultingfilm are reduced.

As pointed out above, in this invention, by incorporating in thebisphenol type epoxy resin a suitable amount of at least one memberselected from the group consisting of the additive epoxy resins (1) to(3), each of which has a compatibility with the bisphenol type epoxyresin and a structure similar to that of the bisphenol type epoxy resinbut is quite different therefrom in a part of the structure, it is madepossible to inhibit arrangement of the bisphenol type epoxy resinmolecules, which results in crystallization, and thus preventcrystallization even at low temperatures.

The above-mentioned bisphenol type epoxy resin or its mixture with theabove-mentioned additive epoxy resin (1), (2) or (3) is emulsified inwater with a nonionic surface active agent according to customaryprocedures.

As the non-ionic surface active agent, there can be mentioned, forexample, surface active agents of the alkylaryl ether type having an HLBvalue of 10.9 to 19.5, such as polyoxyethylene nonyl phenyl ether andpolyoxyethylene octyl phenyl ether, surface active agents of the alkylether type having an HLB value of 10.8 to 16.5, such as polyoxyethylenelauryl ether and polyoxyethylene oleyl ether, surface active agents ofthe alkyl ester type having an HLB value of 9.0 to 16.5, such aspolyoxyethylene laurate, polyoxyethylene oleate and polyoxyethylenestearate, and surface active agents of the polyoxyethylene benzylatedphenyl type having an HLB value of 9.2 to 18.

As another means for attaining the object of preventing crystallization,in this invention there can be adopted use of a polyoxyethylenebenzylated phenyl ether having the structure ##SPC3## and an HLB valueof at least 15 as a surface active agent for emulsifying the abovebisphenol type epoxy resin or its mixture with the additive epoxy resinin water.

As the polyoxyethylene benzylated phenyl ether, there can be used, forexample, such commercially available products as Newcoal 714 (HLD - 15)and Newcoal 723 (HLB = 16.6) (trademarks for products manufactured byNippon Nyukazai Co., Ltd.), and Emulgen A-500 (HLB = 18) (trademark forthe product manufactured by Kao-Atlas Co., Ltd.).

For emulsification of the epoxy resin, the polyoxyethylene benzylatedphenyl ether having an HLB value of at least 15 is used in an amount of0.1 to 20% by weight based on the epoxy resin.

A polyoxyethylene benzylated phenyl ether having an HLB value notexceeding 15 does not have sufficient effect, and even if prevention ofcrystallization is attained by the use of such ether to some extent, theeffect is retained only for about 30 days at longest.

As pointed above, undesired phenomenon of crystallization can beeffectively prevented in this invention by adding to the bisphenol typeepoxy resin at least one member selected from the group consisting ofthe above additive resins (1) to (3) having a compatibility with thebisphenol type epoxy resin and a structure similar to that of thebisphenol type epoxy resin but being quite different therefrom in a partof the structure, or by emulsifying the bisphenol type epoxy resin inwater with a polyoxyethylene benzylated phenyl ether having an HLB valueof at least 15. If the above two means are adopted in combination, thecrystallization-preventing effect can be greatly enhanced.

In the composition of this invention, a curing agent should be added inorder to cure the above-mentioned epoxy resin. As the curing agent,there can be employed known compounds such as water-soluble andwater-dispersible polyamide resins, amine adducts, polyamines and thelike.

When it is intended to improve the film-forming property especiallyunder high-humidity conditions, good results are obtained when apolyamide resin prepared from a dimer acid and a polyether diamine,preferably such polyamide resin having an amine value of 250 to 500, isemployed as the curing agent.

The dimer acid to be used for forming the above polyamide resin is aproduct prepared by employing an unsaturated fatty acid having 18 carbonatoms as the starting material, and the product is composed mainly of adimer acid and includes small amounts of a trimer acid and a monomeracid. As the polyether diamine to be used for forming the abovepolyamide resin, there can be mentioned, for example, ##STR1##

The intended polyamide resin can be obtained by reacting such polyetherdiamine wit the dimer acid at 150 to 250°C. for 1 to 4 hours accordingto customary procedures.

In this invention, the intended polyamide resin, preferably having anamine value of 250 to 500, can also be prepared by substituting a partof the polyether diamine by one or more of aliphatic amines such as##STR2## It is preferred that the aliphatic amine be used in an amountof 0.1 to 4 moles per mole of the polyether diamine.

In order to increase the molecular weight of the polyamide resin curingagent, it is possible to add and react a chain extender at the reactionbetween the dimer acid and polyether diamine or the reaction among thedimer acid, polyether diamine and aliphatic amine. As the chainextender, there can be used, for example, acrylonitrile, methylmethacrylate, formaldehyde, a polyglycol type epoxy resin, a glycerintype epoxy resin or the like. When the so obtained high-molecular-weightpolyamide resin, preferably having an amine value of 250 to 500, is usedas the curing agent, the resulting composition has very excellentfilm-forming properties under high-humidity conditions and gives a filmvery excellent in anti-cracking properties.

Further, an aromatic amine compound can be used in combination with theabove polyamide resin. As such aromatic amine compound, the followingcompounds can be mentioned: (1) Aromatic amines having a structure suchas shown below (when these amines are solid at room temperature, theyare used in the state melt-mixed with the above polyamide resin or othercuring agent mentioned below): ##SPC4## ##SPC5##

2. Reaction products between an aromic amine and an epoxy resin obtainedaccording to customary procedures (aromatic amine adducts).

3. Polyamide resins prepared by employing an aromatic amine.

When such aromatic amine compound is used in combination with theabove-mentioned polyamide resin curing agent, the moisture resistance,saline dipping resistance and salt spraying resistance are highlyimproved in the resulting film.

It is preferred that the ratio of the above aromatic amine to thepolyamide resin derived from a dimer acid and a polyether diamine bewithin a range of from 5/95 to 50/50 as expressed in the non-volatilecomponent weight ratio.

The so obtained curing agent or curing agent composition is mixed withan epoxy resin emulsion according to customary procedures to form anaqueous epoxy resin paint composition of this invention.

In this invention, it is preferred that the mixing ratio of the epoxyresin and curing agent be such that the ratio of the epoxy groups to theactive hydrogen group is within a range of from 0.5 to 1.5.

The aqueous epoxy resin paint composition of this invention may furthercomprise additives customarily used in this field, such as organicpigments, inorganic pigments, surface active agents, thickeners and thelike.

In case use of a conventional anti-corrosive pigment of the chromatetype is restricted because of the toxicity of chromium ions dissolvedout of the film, it is preferred that at least one member selected fromthe group consisting of molybdic acid salts of strontium, calcium,potassium, iron (divalent), barium and ammonium be used instead of thechromate type anti-corrosive pigment.

The molybdate type anti-corrosive pigment is nontoxic and its corrosionresistance is superior or comarable to that of the conventional chromatetype anti-corrosive pigment, and it is further characterized in that itpromotes the film-forming property of the resulting composition underhigh-humidity conditions and even when the composition is applied in alarge thickness, the curing is accomplished uniformly throughout thefilm so that the degree of curing does not differ between the surfaceportion and the interior of the film (this property will hereinafter bereferred to as "curing uniformity").

It is preferred that this molybdate type anti-corrosive pigment beincorporated in the paint composition in an amount of 0.1 to 20% byweight. If the amount incorporated of the pigment is smaller than 0.1%by weight, no substantial anti-corrosive effect is obtained and thefilm-forming property under high-humidity conditions is not promoted. Incontrast, if the amount incorporated of the pigment is larger than 20%by weight, the pigment concentration increases and tendency of reductionof physical properties of the film is observed.

In view of the rust-preventive effect and from the economical viewpoint,it is especially preferred that the molybdate type anti-corrosivepigment be incorporated in an amount of 5 to 10% by weight.

It has been found that especially good results are obtained when amongthe foregoing molybdate type anti-corrosive pigments, strontiummolybdate or calcium molybdate obtained by calcining a mixture ofmolybdenum oxide and calcium carbonate or strontium carbonate at 600° to800°C. is chosen and used.

In the aqueous epoxy resin paint composition of this invention, at thetime of application the main components (the epoxy resin emulsion, thepigment, etc.) are mixed with the curing agent, the mixture is dilutedappropriately with water and the resulting dilution can be applied to asubstrate to be coated according to customary coating methods, forexample, brush-coating, spray-coating and air spray-coating methods.Since the paint composition of this invention has a very highthixotropic property, a thick coating having a thickness of more than100 μ can be obtained by one coating.

This invention will now be illustrated in more detail by reference tothe following Examples, in which all of "parts" and "%" are by weight.

EXAMPLE 1

In a main component comprising 10 parts of red iron oxide, 35 parts oftalc, 34 parts of water, 20 parts of a bisphenol type epoxy resin(Epikote 828 having an epoxy equivalent of 190) and 2 parts ofpolyoxyethylene laurate (Newcol 150 having an HLB value of 10.5 trademark for the product manufactured by Nippon Nyukazai Co., Ltd.), aportion of the Epikote 828 was replaced by an epoxy resin having asimilar structure, which is indicated in Table 1, and it was examinedthe state of formation and growth of crystals.

                                      Table 1                                     __________________________________________________________________________            Additive Resin              State of Formation and                    Sample       Kind       Amount                                                                            Epikote 828                                                                           Growth of Crystals.sup.1)                                                                  Remarks                      __________________________________________________________________________            (methyl-substituted bisphenol                                                 epoxy resin)                                                          Comparative                                                                           Epiclon 800 (having epoxy   observed                                  Sample No. 1                                                                          equivalent of 195-225)                                                                        1%  99%     (after 10 days)                                                                            comparison                   Sample No. 1                                                                              "           2%  98%     not observed this invention               Sample No. 2                                                                              "           5%  95%     not observed this invention               Sample No. 3                                                                              "           10% 90%     not observed this invention                       (novolak type epoxy resin)                                            Comparative                                                                           Epikote 152 (having epoxy   observed                                  Sample No. 2                                                                          equivalent of 172-179)                                                                        1%  99%     (after 10 days)                                                                            comparison                   Sample No. 4                                                                          ditto           10% 90%     not observed this invention                       (dimer acid type epoxy resin)                                                 Epikote 871 (having epoxy                                             Sample No. 5                                                                          equivalent of 390-470)                                                                        10% 90%     not observed this invention               __________________________________________________________________________     Note:                                                                         .sup.1) The above main component was placed in a can and the can was          sealed and allowed to stand still in a thermostat chamber maintained at 0     to 5°C. for 6 months. Then, the can was opened. The case where         glittering crystals were floating on the paint surface is indicated as        "observed" and the case where no crystals were formed is indicated as "no     observed". The upper portion of the paint in which crystals were formed       was ladled out and washed with water, and the residue was examined with a     microscope to confirm formation of crystals. (In the subsequent Examples,     the state of formation and growth of crystals was examined by the above       method.)                                                                 

As is apparent from the results shown in Table 1, in the componentshaving a composition specified in this invention formation of crystalswas not observed for as long as 6 months or more and they had a veryexcellent storage stability. When a curing agent was incorporated intoeach of these main components and the paint compositions were applied toa substrate, there were obtained films which were superior or comparableto films formed from ordinary aqueous epoxy resin paints with respect tosuch properties as the water resistance, chemical resistance, corrosionresistance and the like.

When a polyamide resin derived from a dimer acid and a polyetherdiamine, for example, a polyamide resin of an amine value of 350 formedby condensing 1 mole of a dimer acid and 12 moles of H₂ N--(CH₂)₃--O--(CH₂)₃ --NH₂, or a mixture formed by mixing the above polyamideresin at a mixing weight ratio of 1:1 with an amine adduct obtained byreacting a bisphenol type epoxy resin (Epikote 828) and metaphenylenediamine at a mole ratio of 2:1, was used as the curing agent and thiscuring agent was mixed with the main component so that the epoxy groupsin the emulsion and the active hydrogen groups in the curing agent wereequivalent to each other, a very excellent film-forming property underhigh-humidity conditions was attained and a film having excellentchemical and physical properties was obtained.

In compositions shown in Table 1, in order to evaluate thecrystallization-preventing effect, the formulation of components wasmade almost equal in each composition, but it was confirmed that similarresults were obtained when other epoxy resins were used or ordinaryorganic or inorganic pigments or the like were incorporated.

EXAMPLE 2

20 parts of a bisphenol type epoxy resin (DER 331) was emulsified inwater with a polyoxyethylene benzylated phenyl ether having an HLB valueof 15 (Newcol 174), and 10 parts of red iron oxide and 35 parts of talcwere added to the emulsion according to a customary method. The state offormation and growth of crystal in the main component (sample No. 6) wasexamined. For comparison, a main component (comparative sample No. 3)was prepared in the same manner as above except that polyoxyethylenelaurate having an HLB value of 10.5 was used instead of thepolyoxyethylene benzylated phenyl ether, and the state of formation andgrowth of crystals was examined. Results are shown in Table 2.

                  Table 2                                                         ______________________________________                                                    State of Formation and                                            Sample      Growth of Crystals                                                                              Remarks                                         ______________________________________                                        Sample No. 6                                                                              not observed     this invention                                   Comparative Sample                                                                        observed (crystals were                                                                        comparison                                                   formed after passage of                                                       10 days                                                           ______________________________________                                    

The curing agent prepared in Example 1 was mixed with the main componentof this invention to form an aqueous epoxy resin paint composition. Afilm obtained from the paint composition has an excellent chemical andphysical properties.

EXAMPLE 3

The state of formation and growth of crystals was examined with respectto main components prepared in the same manner as in Example 2 exceptthat a polyoxyethylene benzylated phenyl ether having an HLB indicatedin Table 3 was used for emulsifying the bisphenol type epoxy resin.Results are shown in Table 3.

                                      Table 3                                     __________________________________________________________________________            HLB and Trade                                                                            State of Forma-                                                    Name of Surface                                                                          tion and Growth                                            Sample  Active Agent                                                                             of Crystals                                                                             Remarks                                          __________________________________________________________________________    Comparative                                                                           9.2        observed                                                   Sample No. 4                                                                          (Newcol 704*)                                                                            (after 10 days)                                                                         comparison                                       Comparative                                                                           12.5       observed                                                   Sample No. 5                                                                          (Newcol 707*)                                                                            (after 20 days)                                                                         comparison                                               15                   this                                             Sample No. 7                                                                          (Newcol 714*)                                                                            not observed                                                                            invention                                                16.6                 this                                             Sample No. 8                                                                          (Newcol 723*)                                                                            not observed                                                                            invention                                                18                   this                                             Sample No. 9                                                                          (Emulgen A-500**)                                                                        not observed                                                                            invention                                        __________________________________________________________________________     *Manufactured by Nippon Nyukazai Co., Ltd.                                    **Manufactured by Kao-Atlas Co., Ltd.                                    

The curing agent prepared in Example 1 was mixed with the each maincomponent of this invention to form a aqueous epoxy resin paintcomposition. A film obtained from the each paint composition has anexcellent chemical and physical properties.

EXAMPLE 4

A methyl-substituted bisphenol resin (Epiclon 800 having an epoxyequivalent of 195 to 225), a novolak type epoxy resin (Epikote 152having a epoxy equivalent of 172 to 179) or a dimer or trimer acid typeepoxy resin (Epikote 871 having an epoxy equivalent of 390 to 470) wasincorporated into a bisphenol type epoxy resin (Epikote 828) in anamount indicated in Table 4. 20 parts of the so prepared resin mixturewas emulsified in 5 parts of water with a polyoxyethylene benzylatedphenyl ether having an HLB value of 16.6. The so obtained emulsion wasmixed with a composition comprising 10 parts of red iron oxide, 35 partsof talc and 30 parts of water to form a main component.

The state of formation and crystals was examined with respect to each ofthe so obtained component to obtain results shown in Table 4.

From the results obtained in Examples 2, 3 and 4, it will readily beunderstood that in this invention crystallization can be effectivelyprevented by using a specific surface active agent and this effect canbe further enhanced by using an epoxy resin of a specific structure incombination with the bisphenol type epoxy resin.

1 mole of a dimer acid was mixed with 12 moles of a polyether diaminehaving a structural formula of H₂ N--(CH₂)₃ --O--(CH₂)₃ --NH₂, and themixture was subjected to condensation reaction at 160°C. When thereaction had consumed all water present, the temperature was furtherelevated to 200° to 250°C and the condensation product was maintained atthis temperature for 3 hours, to obtain a polyamide resin of an aminevalue of 350 to be used as a curing agent.

The so obtained curing agent was incorporated into the main component ofthe above sample No. 10, 14 or 17 so that the ratio of the epoxy groupsto the active hydrogen groups was 1.0. Each paint exhibited a veryexcellent firmforming property even when applied under high-humidityconditions and gave a film excellent in both physical and chemicalproperties.

                                      Table 4                                     __________________________________________________________________________             Additive Resin                                                                            Amount of                                                                             State of Formation and                           Sample   Kind    Amount                                                                            Epikote 828                                                                           Growth of Crystals*                                                                        Remarks                             __________________________________________________________________________    Sample No. 10                                                                          Epiclon 800                                                                            2% 98%     not observed this invention                      Sample No. 11                                                                            "      5% 95%     not observed this invention                      Sample No. 12                                                                            "     10% 90%     not observed this invention                      Sample No. 13                                                                          Epikote 152                                                                            5% 95%     not observed this invention                      Sample No. 14                                                                            "     10% 90%     not observed this invention                      Sample No. 15                                                                            "     15% 85%     not observed this invention                      Sample No. 16                                                                          Epikote 871                                                                           10% 90%     not observed this invention                      Sample No. 17                                                                            "     15% 85%     not observed this invention                      Sample No. 18                                                                            "     20% 80%     not observed this invention                      __________________________________________________________________________     Note:                                                                         *The state of formation and growth of crystals was examined after samples     were allowed to stand still for 12 months under the same conditions as        described in Example 1.                                                  

EXAMPLE 5

A main component was prepared by incorporating 10 parts of red ironoxide, 20 parts of talc, 12 parts of calcium carbonate and 30 parts ofwater into an epoxy resin emulsion comprising 27 parts of a bisphenolepoxy resin (having an epoxy equivalent of 190), 6 parts of apolyoxyethylene benzylated phenyl ether having an HLB value of 12 and 6parts of water. Then, 12 parts of the polyamide resin curing agentprepared in Example 4 was mixed with 88 parts of the so obtained maincomponent (sample No. 19). The curing property (the degree of hardeningobserved when the sample was charged into a certain vessel, the vesselwas sealed and the sample was allowed to stand still in this state forone week) and film-forming properties under high-humidity conditions(degree of curing observed when the sample was applied to the innersurface of a certain vessel, the vessel was sealed and the coated samplewas allowed to stand still for one week) were examined to obtain resultsshown in Table 5.

EXAMPLE 6

In the same manner as described in Example 5, polyamide resins having anamine value of 320 or 290 were prepared by reacting 1 mole of a dimeracid with 10 or 8 moles of a polyether diamine having a structure of##STR3## These polyamide resins were mixed with the main componentobtained in Example 5 at mixing ratios of 10:90 (sample No. 20) and15:85 (sample No. 21), respectively. Then, the curing property andfilm-forming property under high-humidity conditions were examined toobtain results shown in Table 5.

EXAMPLE 7

1 mole of a dimer acid was mixed with 3 moles of a polyether diamine [H₂N(CH₂)₃ --O--(CH₂)₃ --NH₂ ] and 7 moles of an aliphatic amine(triethylene tetraamine), and 5 moles of methyl methacrylate and 0.3mole of a polyglycol type epoxy resin (product manufactured and soldunder tradename "Eponitt 014" by Nitto Kasei Co., Ltd.) were added aschain extenders to the mixture. In the same manner as described inExample 4, the mixture was reacted under heating to obtain a polyamideresin having an amine value of 442.

The so-obtained resin was mixed with the main component prepared inExample 5 at a prescribed mixing ratio (sample No. 22), and theresulting composition was subjected to the above-mentioned comparativetests to obtain results shown in Table 5.

EXAMPLE 8

In the same manner as described in Example 7, polyamide resins wereprepared by using components shown below, and each polyamide resin wasmixed with the main component prepared in Example 5 and the compositionwas subjected to the above-mentioned comparative tests to obtain resultsshown in Table 5.

Sample No. 23:

1 mole of a dimer acid, 5 moles of triethylene tetraamine, 3 moles of apolyether diamine ##STR4## 4 moles of methyl methacrylate and 0.25 moleof Eponitt 014.

The obtained polyamide resin had an amine value of 405.

Sample No. 24:

1 mole of a dimer acid, 12 moles of polyether diamine ##STR5## 5 molesof methyl methacrylate and 1 mole of a glycerin type epoxy resin(Epikote 812 having an epoxy equivalent of 150 to 170).

The obtained polyamide resin had an amine value of 293.

Sample No. 25:

1 mole of a dimer acid, 10 moles of a polyether diamine [NH₂ --(CH₂)₃--O--(CH₂)₃ --O--(CH₂)₃ --NH₂ ], 4 moles of methyl methacrylate and 3moles of formaldehyde.

The obtained polyamide resin had an amine value of 289.

Sample No. 26:

1 mole of a dimer acid, 6 moles of a polyelther diamine [NH₂ --(CH₂)₃--O--(CH₂)₂ --O--(CH₂)₃ --NH₂ ], 4 moles of triethylene tetraamine, 4moles of methylacrylate and 0.5 mole of Epikote 812.

The obtained polyamide resin had an amine value of 378.

Example 9

A bisphenol type epoxy resin (Epikote 828 having an epoxy equivalent of184 to 194) was reacted with metaphenylene diamine at a mole ratio of2:1 to obtain an amine adduct.

The amine adduct was used in combination with the polyamide resinobtained in Example 7 at a prescribed mixing ratio (samples No. 27 andNo. 28), and the results of comparative tests are shown in Table 6. Forcomparison, results obtained when the above amine adduct alone was usedas the curing agent are also shown in Table 6 (comparative sample No.6).

EXAMPLE 10

Results obtained when a part of the polyamide resin obtained in Example7 was replaced by metaphenylene diamine are shown in Table 6 (sample No.29).

EXAMPLE 11

A dimer acid was reacted with metaphenylene diamine according to acustomary method to obtain a polyamide resin. Results obtained when theso-obtained resin was used in combination with the polyamide resinobtained in Example 7 at a prescribed mixing ratio (samples No. 30 andNo. 31) and results obtained when the above resin prepared from a dimeracid and methaphenylene diamine alone was used as the curing agent(comparative sample No. 7) are shown in Table 6.

For comparison, in the same manner as in Example 7, polyamide resinswere prepared from components shown below, and each of the so obtainedpolyamide resins was mixed with the above-mentioned main component andthe resulting composition was subjected to comparative tests to obtainresults shown in Table 5.

Comparative Sample No. 8:

1 mole of a dimer acid, 10 moles of metaxylene diamine, 4 moles ofmethacrylate and 0.5 mole of Epikote 812.

The obtained polyamide resin had an amine value of 302.

Comparative Sample No. 9:

1 mole of a dimer acid, 15 moles of metaxylene diamine and 4 moles ofmethyl methacrylate.

The obtained polyamide resin had an amine value of 383.

Comparative Sample No. 10:

15 moles of metaxylene diamine, 7 moles of methyl methacrylate and 1mole of Epikote 812.

The obtained resin had an amine value of 454.

Comparative Sample No. 11:

1 mole of a dimer acid and 3 moles of triethylene tetraamine.

The obtained polyamide resin had an amine value of 420.

From the foregoing results of the comparative tests, it will readily beunderstood that the paint composition of this invention has an excellentfilm-forming property under high-humidity conditions and it can readilybe cured under such conditions where water is present. Accordingly, thepaint composition of this invention can provide a film of sufficientproperties even when applied in a sealed chamber or on the inner face ofa sealed tank.

When the paint composition is applied in an ordinary state (underlow-humidity conditions or under a current of air), it can provide afilm having properties superior or comparable to those of films preparedfrom conventional paints.

With respect to the above samples No. 21, No. 25, No. 26, No. 27, No.28, No. 29, No. 30 and No. 31, a polyoxyethylene benzylated phenyl etherhaving an HLB value of 16.6 was used for emulsifying the epoxy resin inwater and the above comparative tests were conducted. It was found thatin each case a paint of a good storage stability in which no crystalswere formed at low temperatures was obtained.

                                      Table 5                                     __________________________________________________________________________    Results of Comparative Tests                                                           Main Component/Curing                                                                      Curing Property of Result-                                                                   Film-Forming Property under              Sample   Agent Mixing Ratio                                                                         ing Paint Composition.sup.1)                                                                 High-Humidity Conditions.sup.2)                                                                Remarks                 __________________________________________________________________________    Sample No. 19                                                                          88/12        good           good             this invention          Sample No. 20                                                                          90/10        good           good             this invention          Sample No. 21                                                                          85/15        good           good             this invention          Sample No. 22                                                                          90/10        good           good             this invention          Sample No. 23                                                                          90.6/9.4     good           good             this invention          Sample No. 24                                                                          87.4/12.6    good           good             this invention          Sample No. 25                                                                          86/14        good           good             this invention          Sample No. 26                                                                          90/10        good           good             this invention          Comparative                                                                   Sample No. 8                                                                           88/12        bad            bad              comparison              Comparative                                                                   Sample No. 9                                                                           91.4/8.6     bad            bad              comparison              Comparative                                                                   Sample No. 10                                                                          92.4/7.6     bad            bad              comparison              Comparative                                                                   Sample No. 11                                                                          88.8/11.2    somewhat good  bad              comparison              __________________________________________________________________________     Notes:                                                                        .sup.1) After the main component was mixed with the curing agent, a           prescribed amount of the resulting composition was immediately charged in     a polyethylene cup, and the composition was allowed to stand still in the     sealed state for one week. Then, the polyethylene cup was stripped off to     separate the inside solid from the vessel. The solid was cut into halves      with a knife to examine whether or not the outer portion and the interior     of the solid was completely cured. The case where both the outer portion      and the interior were completely cured is indicated as "good". The case       where the resulting solid was soft and rubber-like is indicated as "bad",     and the case where the degree of curing was different between the outer       portion and the interior is indicated as "somewhat good".                     .sup.2) After the main component was mixed with the curing agent, the         composition was applied to the inner face of a metal can and the can was      immediately sealed. The coated composition was allowed to stand still in      this state for one week. Then, the can was opened and the condition of th     film was examined with fingers. The case where no abnormality was felt is     indicated as "good", and the case where the film was viscous or it adhere     to fingers is indicated as "bad".                                        

                                      Table 6                                     __________________________________________________________________________    Results of Comparative Tests                                                                 Film-Forming                                                                           Properties of film (150 μ thick film)                       Mixing                                                                              Property under                                                                         Saline                                                                              Salt                                                     Weight                                                                              High-Humidity                                                                          Dipping                                                                             Spraying                                                                             Moisture                                 Sample   Ratio.sup.1)                                                                        Conditions                                                                             Test.sup.2)                                                                         Test.sup.3)                                                                          Resistance.sup.4)                                                                     Remarks                          __________________________________________________________________________    Sample No. 22                                                                          --    good     30 days                                                                             300 hours                                                                            300 hours                                                                             this invention                   Sample No. 27                                                                          80/20 good     60 days                                                                             500 hours                                                                            500 hours                                                                             this invention                   Sample No. 28                                                                          50/50 good     60 days                                                                             500 hours                                                                            500 hours                                                                             this invention                   Sample No. 29                                                                          80/20 good     60 days                                                                             500 hours                                                                            500 hours                                                                             this invention                   Sample No. 30                                                                          80/20 good     60 days                                                                             500 hours                                                                            500 hours                                                                             this invention                   Sample No. 31                                                                          50/50 good     60 days                                                                             500 hours                                                                            500 hours                                                                             this invention                   Comparative                                                                   Sample No. 6                                                                           0/100 bad      not tested because no film was formed                                                              comparison                       Comparative                                                                   Sample No. 7                                                                           0/100 bad      not tested because no film was formed                                                              comparison                       __________________________________________________________________________     Notes:                                                                        .sup.1) ratio of (polyamide resin derived from dimer acid and polyether       diamine)/(aromatic amine adduct, aromatic amine or polyamide resin formed     by employing aromatic amine)                                                  .sup.2) dipped in 3% aqueous solution of NaCl                                 .sup.3) 5% aqueous solution of NaCl was sprayed at 35°C.               .sup.4) measured at temperature of 50°C. and relative humidity of      100%                                                                     

Example 12

9 parts of red iron oxide, 10 parts of talc, 9 parts of strontiummolybdate and 30 parts of water were kneaded. Then, the kneaded mixturewas mixed with an epoxy resin emulsion formed by emulsifying 20 parts ofa bisphenol type epoxy resin in 7 parts of water with 2 parts of apolyoxyethylene benzylated phenol ether having an HLB value of 16.6 toform a main component.

A polyamide curing agent having an amine value of 320 was prepared bycondensing 1 mole of a dimer acid with 10 moles of a polyether diamine[H₂ N--(CH₂)₂ --O--(CH₂)₂ --(CH₂)₂ --NH₂ ] at 160°C according to acustomary method and reacting the condensate at 200° to 250°C.

The above main component was mixed with the so obtained curing agent ata mixing weight ratio of 90/10 to form a paint composition of thisinvention. The paint composition was applied to a substrate in athickness of 170 μ and naturally dried for one week. The resulting filmwas subjected to various comparative tests to obtain results shown inTable 7.

EXAMPLE 13

An anti-corrosive paint composition was prepared in the same manner asin Example 12 except that a polyamide derived from 1 mole of a dimeracid, 7 moles of triethylene tetraamine and 3 moles of a polyetherdiamine ##STR6## was used as the curing agent, and 7 parts of calciummolybdate and 13 parts of talc were employed.

EXAMPLE 14

In the main component of Example 12, the epoxy resin was replaced bythat used in sample No. 12 of Example 4, 5 parts of calcium molybdatewas used as the anti-corrosive pigment and the amount of talc waschanged to 15 parts. Crystallization at low temperatures was not causedat all in the resulting aqueous epoxy resin emulsion.

A mixture of the polyamide resin obtained in Example 12 with an aromaticamine adduct was used as the curing agent.

The main component was mixed with the curing agent so that the epoxygroups in the emulsion and the active hydrogen atom groups in the curingagent were equivalent to each other. The resulting paint composition wastested to comparative tests to obtain results shown in Table 7.

Example 15

In the main component of Example 12, the amount of talc was changed to13 parts and 5 parts of potassium molybdate was used as theanti-corrosive pigment.

1 mole of a dimer acid, 7 moles of triethylene tetraamine, 3 moles of apolyether diamine [H₂ N--(CH₂)₃ --O--(CH₂)₃ --NH₂ ], 5 moles ofmethylmethacrylate and 0.3 mole of a polyglycol type epoxy resin(Eponitt 014) were reacted in the same manner as in Example 12 to obtaina polyamide resin having an amine value of 442, which was used as acuring agent.

The above main component was mixed with the so obtained curing agent ata mixing weight ratio of 90/10 to obtain an anti-corrosive paintcomposition.

EXAMPLE 16

An anti-corrosive paint composition was prepared in the same manner asin Example 15 except that 5 parts of barium molybdate was used as theanti-corrosive pigment. The resulting composition was subjected tocomparative tests to obtain results shown in Table 7.

EXAMPLE 17

In the main component of Example 12, the epoxy resin was replaced bythat used in sample No. 14 of Example 4 and it was mixed with 9 parts ofred iron oxide, 15 parts of talc and 2 parts of ammonium molybdate.

20% by weight of the polyamide resin prepared in Example 15 was replacedby an amine adduct obtained by reacting a bisphenol type epoxy resin(Epikote 828) with metaphenylene diamine at a ratio of 1:2, and theresulting mixture was used as a curing agent.

The above main component was mixed with the curing agent so that theepoxy groups in the emulsion and the active hydrogen atom groups in thecuring agent were equivalent to each other to obtain an aqueous epoxyresin paint composition.

EXAMPLE 18

An aqueous epoxy resin paint composition was prepared in the same manneras in Example 14 except that the epoxy resin was replaced by that usedin sample No. 17 of Example 4, the amount of talc was changed to 15parts and 5 parts of strontium molybdate was used as an anti-corrosivepigment.

EXAMPLE 19

An aqueous epoxy resin paint composition was prepared in the same manneras in Example 12 except that a mixture of 3 parts of strontium molybdateand 5 parts of calcium molybdate was used as an anti-corrosive pigment.

EXAMPLE 20

An aqueous epoxy resin paint composition was prepared in the same manneras in Example 12 except that 9 parts of iron (divalent) molybdate wasused as an anti-corrosive pigment.

Comparisons Comparative Sample No. 10:

The aqueous epoxy resin emulsion of Example 12 was mixed with 16 partsof talc and 9 parts of red iron oxide to form a main component, whichwas then mixed with an ordinary aliphatic amine adduct as a curingagent, to obtain a paint composition.

Comparative Sample No. 11:

The aqueous epoxy resin emulsion of Example 12 was mixed with 9 parts ofred iron oxide, 10 parts of talc, 10 parts of strontium chromate and 30parts of water to form a main component, which was then mixed with thesame curing agent as used in comparative sample No. 10, to obtain ananti-corrosive paint composition.

Comparative Sample No. 12:

The aqueous epoxy resin emulsion of Example 12 was kneaded with 9 partsof red iron oxide, 10 parts of talc, 10 parts of zinc borate and 30parts of water to form a main component, which was then mixed with thesame curing agent as used in comparative sample No. 10, to obtain apaint composition.

                                      Table 7                                     __________________________________________________________________________    Results of Comparative Tests                                                            Film-Forming Property                                                                      Curing Uniformity                                                                        Salt Spray-                                                                           Moisture                                                                             Saline                                                                              Water                  Sample    under High-Humidity.sup.1)                                                                 of Film.sup.2)                                                                           ing Test.sup.3)                                                                       Resistance.sup.4)                                                                    ping Test.sup.5)                                                                    Resistance.sup.6)      __________________________________________________________________________    (This Invention)                                                              Example 12                                                                    Example 13                                                                    Example 14                                                                    Example 15                                O                                   Example 16                                                                    Example 17                                O                                   Example 18                                                                    Example 19                                                                    Example 20                                                                    (Comparisons)                                                                 Comparative                                                                   Sample No. 10                                                                           X            X          X       X      Δ                                                                             O                      Comparative                                                                   Sample No. 11                                                                           X            X                                                      Comparative                                                                   Sample No. 12                                                                           X            X          O       O                                   __________________________________________________________________________      : very good, O: good, Δ: somewhat bad, X:bad?                           Notes:                                                                       .sup.1) After the main component was mixed with the curing agent, the         composition was applied on the inner face of a certain vessel and the fil     was allowed to stand still in the sealed state for 7 days. After passage      of 7 days the vessel was opened and the state of the film was examined        with the fingers. Namely, it was checked whether the film was sticky or       the film adhered to the fingers.                                              .sup.2) The paint was coated in a thickness of about 1 cm on a substrate,     and after passage of 7 days, the film was cut with a knife to examine the     curing uniformity.                                                            .sup.3) A 3% aqueous solution of NaCl was sprayed at 35°C. for 500     hours.                                                                        .sup.4) The film was allowed to stand still at a temperature of               50°C. and a relative humidity of 100% for 500 hours.                   .sup.5) The film was immersed in a 5% aqueous solution of NaCl for 30         days.                                                                         .sup.6) The film was immersed in water for 30 days.                      

From the foregoing results of the comparative tests, it will readily beunderstood that the paint composition of this invention is superior orcomparable to paint compositions comprising a conventional strontiumchromate type pigment in respect to the anti-corrosive property, andthat the paint composition of this invention is much superior to suchconventional paint compositions in the film-forming property underhigh-humidity conditions and the curing uniformity.

What is claimed is:
 1. An aqueous epoxy resin paint compositioncomprising an epoxy resin emulsion formed by emulsifying in water (A) 98to 50% by weight of a bisphenol type epoxy resin and (B) 2 to 50% byweight of methyl-substituted bisphenol epoxy resins, with a non-ionicsurface active agent, and a curing agent incorporated in said epoxyresin emulsion.
 2. An aqueous epoxy resin paint composition as set forthin claim 1 wherein the non-ionic surface active agent is apolyoxyethylene benzylated phenyl ether having an HLB value of at least15.
 3. An aqueous epoxy resin paint composition as set forth in claim 1wherein the curing agent is a polyamide resin derived from a dimer acidand a polyether diamine.
 4. An aqueous epoxy resin paint composition asset forth in claim 1 wherein the curing agent is a mixture, the majorpart of which is a polyamide resin derived from a dimer acid and apolyether diamine and the minor part of which is an aromatic aminecompound.
 5. An aqueous epoxy resin paint composition as set forth inclaim 1 wherein the curing agent is a mixture, the major part of whichis a polyamide resin derived from a dimer acid, polyether diamine and achain extender and/or an aliphatic amine and the minor part of which isan aromatic amine compound.
 6. An aqueous epoxy resin paint compositionas set forth in claim 1 which further comprises 0.1 to 20% by weight ofat least one member selected from the group consisting of molybdic acidsalts of strontium, calcium, potassium, iron (divalent), barium andammonium.
 7. An aqueous epoxy resin paint composition which comprises anepoxy resin emulsion formed by emulsifying a mixture comprising (A) 98to 50% by weight of a bisphenol type epoxy resin and (B) 2 to 50% byweight of methyl-substituted bisphenol epoxy resins in water with apolyoxyethylene benzylated phenyl ether having an HLB value of at least15 and a curing agent which is a polyamide resin derived from a dimeracid and a polyether diamine.